Patent Citation 1 discloses a dump truck. This dump truck is provided with a pair of left and right front wheels, a pair of left and right rear wheels, a frame, an operator's cab arranged on the frame at a front position thereof, and a body arranged on the frame.
Patent Citation 2 shows a body for a dump truck, which is constructed as described above. This body includes a body frame, and a bottom wall, front wall and left and right side walls arranged on the body frame. Defined by the bottom wall, front wall and left and right side walls is a payload section in which an object to be hauled such as earth or sand, that is, a payload is loaded. Many stiffeners are installed at positions on outer sides of the payload section. These stiffeners are installed extending in vertical directions or horizontal directions of the associated ones of the bottom wall, front wall and left and right side walls defining the payload section, and are reinforcing these walls.
Patent Citation 3 shows a construction in which sloping devices are provided in corner parts of a bottom wall forming a payload section of a body for a dump truck. These sloping devices make up earth/sand anti-sticking devices that prevent sticking of earth or sand loaded in the payload section.
In general, a payload such as earth or sand is loaded in a heap in the payload section formed in the body of each dump truck described above, and by the payload, a high load is applied to the body. Rigidity is, therefore, required for the body. To assure this rigidity, many stiffeners are installed on parts of outer sides of the payload section as disclosed in the above-discussed Patent Citation 2.